The present trend in power conversion is to go higher and higher in frequency. Frequencies, such as 0.25-2.0 MegaHertz and higher, have been made possible because of new components which are now available, such as power MOSFETS, better ferrite materials, and quality film capacitors. One of the design approaches in this high frequency field is the resonant converter. The design of a resonant converter requires a high frequency inductor.
In the past, such inductors have been typically fabricated by hand winding Litz wire on a toroidal core. Litz wire is finer than human hair and has no strength. Such prior art high frequency inductor designs result in large amounts of leakage flux, the order of which could be as much as 1.5 to 2.0 times greater than the desired inductance. This variation in leakage flux seriously interferes with production of repeatable designs